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It maybe worth considering a customised bit of drive circuitry; one that pulls in at a high voltage than drops to a lower holding value - or a constant current supply. Both manageable with 'Simple-Switcher' SMPSU devices.
On 19 March 2016 at 12:34, ALANNOTTAGE@...
There could be a case for evaluating that in advance (and maybe with any model?), i.e. powering it up on the bench and checking the temp. rise. It's possible that's how mine failed in it's previous life wherever. It's on a cad-plated steel plate, but not anywhere near as big as below.
From: Paul paul@...
To: ukmicrowaves <ukmicrowaves@...
Sent: Fri, 18 Mar 2016 18:21
Subject: Re: [ukmicrowaves] FS: Transco Y Relay
Follow up to the message I sent a few minutes ago. I also found this
in the instructions for the JWM sequencer, "A word of caution
related to RF relays that are always in a constant energized state.
Most of these relays are not designed to be energized for long
periods of time, and will require a good heatsink to dissipate the
heat that can build up. Transco “Y” relays for example can be
energized for several hours at a time when mounted to an aluminum
plate about 12 inches square or so, by ¼ inch to 3/8 inch thick. To
provide the best possible heat transfer, use transistor thermal
heatsink compound when you mount the relays to the aluminum plate."
Chris made reference to the coil resistance of
the relay. I have an Amphenol relay with a 110VAC
coil. I believe it's R is ~550 ohms. It's not to
hand just now, but I will check it later. Thanks
to Peter for that rule of thumb - I will need to
know that too at some stage!
I don't recall which book/mag/internet
article I was reading recently, Paul (it could
have been the VHF DX manual), but there was
a reference to relay heat sinking. The general
thread was that if the relay was energised for RX,
it would be a good idea to do so.